For years marine biologists have relied on dart biopsies – small portions of tissue obtained by shooting a dart into an animal – to study the genetics of dolphins in the wild. The trouble is that this method can’t be used on very young animals for fear of harming them, and concerns about injury to adult animals has made dart biopsies a controversial choice for field scientists. Now, as reported in the journal PLoS One an international team of marine biologists has found a new way to gather the same information, and it involves little more than collecting a dolphin’s exhaled breath.
As described by University of Queensland scientist Celine Frère and colleagues, the air expelled through dolphin blowholes – simply called “blow” – contains lung surfactant (a mix of proteins and lipids), respiratory fluid, lung cells, and other biological materials. A previous study carried out by C.J. Hogg showed that the presence of reproductive hormones could be detected by analyzing dolphin blow, and subsequent studies have used blow to examine disease in these marine mammals. But the authors behind the new study went in a slightly different direction – if blow is so rich in biological material, might it be useful for genetic studies?
In order to test their hypothesis about dolphin blow, members of the research team used pieces of sterile filter paper stretched over a hoop in an attempt to collect the exhaled residues of wild bottlenose dolphins in Western Australia’s Shark Bay. The basic collection technique worked, and even though extracting the blow from the filter paper turned out to be more difficult than expected, the scientists were able to recover some mitochondrial DNA from one specimen. While the difficulties with the filter paper hampered the laboratory aspect of the study, the scientists were encouraged by the initial result and switched to a different set of subjects thousands of miles from Shark Bay.
Frère and her co-authors turned to the captive bottlenose dolphins held at Baltimore, Maryland’s National Aquarium to refine their technique. Filter paper was ditched as a collection tool in favor of polyproplene tubes which were held upended over the blowholes of six dolphins, and this modified method also proved successful in collecting dolphin blow. In contrast to the meager sample from the pilot study, though, the biological material lining the plastic tubes was rich enough to provide data on mitochondrial DNA and microsatellite DNA from each individual dolphin. Furthermore, the DNA profiles taken from blow matched the DNA profiles of each dolphin taken from blood, suggesting that blow may be just as good as blood for studying dolphin genetics.
Wild dolphins will not just sit still and blow into a tube, however. Adapting the methodology for wild animals presents a substantial challenge, and the authors of the new study state that such efforts are currently underway in Shark Bay. If successful in the field, the new technique would allow scientists to trade in their darts for test tubes.
Frère, C., Krzyszczyk, E., Patterson, E., Hunter, S., Ginsburg, A., & Mann, J. (2010). Thar She Blows! A Novel Method for DNA Collection from Cetacean Blow PLoS ONE, 5 (8) DOI: 10.1371/journal.pone.0012299